Modelling the evolution of the Greenland ice sheet over glacial-interglacial cycles

The Greenland ice sheet (GrIS) formed more than 1 Ma ago and has evolved over many glacial-interglacial cycles. As it still adjusts to past changes, correctly capturing its present-day state is essential to accurately predict its future evolution and contribution to sea level rise. Furthermore, the past offers numerous examples of the GrIS‘ response to warmer climates, possibly analogous to its future fate.

Here, the Parallel Ice Sheet Model (PISM) is utilized to investigate the evolution of the GrIS over past glacial-interglacial cycles. For simulations over such long timescales, the computationally inexpensive PDD scheme is commonly used to calculate surface melt. However, PDD schemes do not capture spatial and temporal differences in surface mass balance sensitivity to temperature and cannot drive glacial-interglacial ice volume changes as they neglect the positive feedback between melt and albedo. To address this, we instead use the Diurnal Energy Balance Model (dEBM-simple) module. It takes into account seasonally and latitudinally varying melt contributions from solar shortwave radiation and changes in albedo in addition to temperature-driven melt to achieve a better representation of orbital timescales.

We calibrate PISM-dEBM-simple with present-day melt rates from the regional climate model RACMO. The calibrated model is then used to investigate the different patterns of growth and retreat of the GrIS over the past glacial-interglacial cycles emerging from using the PDD or the dEBM module in PISM. The enhanced sensitivity of the dEBM to insolation results in an earlier and greater mass loss at the onset of the Holocene, primarily from low-elevation regions and ice shelves.